Ultrasonic waves are produced in two generic forms, transverse and longitudinal. Transverse waves travel across the active surface of the source media and are termed as surface acoustic waves. Longitudinal waves have a wave front that travels normal to the source media. Longitudinal waves fall into two categories, standing waves, and traveling waves. Where an electric periodic wave function signal is applied to a resonant piezoelectric transducer, for example, a reactive mechanical force is derived. If a reflective boundary, i.e., a boundary in the line of travel of the traveling wave that reflects back at least a majority of the wave energy, is placed as to conform to Snell's law, substantial or total internal reflection will be obtained and a steady state standing wave environment is established. In the absence of a reflective boundary, i.e., if the acoustic radiation is propagated to a boundary that passes or absorbs more than half of the incident wave energy, a traveling wave is established, optionally a steady state traveling wave depending on the function of the operating signal generated by the transducer's actuation circuitry.
Fluid-handling devices are known, having a portable, disposable or interchangeable fluid-handling manifold having one or more inlet ports and perhaps one or more outlet ports, providing fluid communication with a fluid duct in the manifold. Such fluid-handling devices may be self-contained or intended for use as a component of a larger system. Known devices of this type having capillary or microfluidic ducts have drawbacks, such as, for example, significant flow resistance and difficulty mixing in the laminar flow regime. Flow is laminar for microfluidics where the Reynolds numbers are less than about 2000, and the lack of turbulence makes mixing difficult. In microfluidic laminar flow, for example, two fluids of different composition can pass side-by-side with little or no intermixing except by diffusion. Rife et al. in U.S. Pat. No. 6,210,128 suggest miniature fluid pumps and mixers having capillary flow lines feeding fluid into large size fluid processing reservoirs. Acoustic radiation is generated to circulate fluid in the reservoirs.
It is an object of the present invention to provide improved fluid-handling apparatus and methods for processing fluid, employing ultrasonic acoustic radiation including at least traveling wave ultrasonic acoustic radiation.